1. Field of the Invention
The present invention relates to novel catalysts for the treatment of gases, in particular industrial gaseous effluents containing sulfur compounds, in order to produce elemental sulfur.
This invention especially relates to novel catalysts for the Claus reaction and/or the hydrolysis reaction of organosulfur compounds.
2. Description of the Prior Art
In the conventional Claus process, to which the present invention is not limited, the recovery of sulfur from gases containing hydrogen sulfide and possibly organosulfur derivatives, comprises two stages.
In a first stage, the hydrogen sulfide is burned in the presence of a controlled amount of air to convert a part of the hydrogen sulfide into sulfur dioxide and then, in a second stage, the resulting gaseous mixture is transferred into converters arranged in series, comprising a catalyst bed, on which the Claus reaction takes place: ##STR1##
In addition to hydrogen sulfide, the gases may contain organic sulfur compounds, such as CS.sub.2 and COS, which are generally stable at the level of catalytic converters and which contribute 20 to 50% of the SO.sub.2 and sulfur compound emissions into the atmosphere following the incineration of the fumes. These very harmful compounds are already contained in the gas to be treated, or are formed in the course of the first oxidation stage.
These compounds may be eliminated by different types of reaction, in particular by hydrolysis according to the reactions (2): EQU CS.sub.2 +2H.sub.2 O.fwdarw.CO.sub.2 +2H.sub.2 S EQU CS.sub.2 +H.sub.2 O.fwdarw.COS+H.sub.2 S EQU COS+H.sub.2 O.fwdarw.CO.sub.2 +H.sub.2 S (2)
These reactions also take place on a catalytic bed, advantageously using a catalyst based on titanium, cerium oxide, zirconium oxide or alumina.
They generally occur simultaneously with the Claus (1) reaction in the converters.
The catalyst beds heretofore employed consisted of catalyst particles in the form of cylindrical or spherical granules formed by molding or extrusion. However, the elemental sulfur production and organic sulfur compound conversion rates obtained with the cylindrical or spherical granules formed by molding or extrusion are lower than the theoretical rates calculated by the laws of thermodynamics.